The creatures that live in Limbo were once people or animals that were living and breathing in the Realm of the Living. When they died, something happened to them so traumatizing that it drove them insane with rage, vengeance, and pain. They lost their minds and humanity and through that their 'Spirit Body' has begun to deteriorate and mutate. They become rotting bodies or skeletons, wraiths, monsters that shouldn't exist. Some change into specific shapes depending on what happened to them, a wife killed by her cheating husband and vowing revenge may become a Wraith, an abandoned abused child may become a Gaki, etc.

The longer they are stuck in Limbo, the stronger their hatred grows. They gain levels through killing each other. They try to kill other people who are new to Limbo and just trying to resurrect themselves out but get more frustrated when they can't; you can only die in Limbo if you have lost your mind with rage and become one of these creatures, so new comers cannot be killed and this drives the creatures even more mad.

The God of Death oversees them, but wishes there were less of them in pain. When new people come here, they must kill these creatures to resurrect themselves, it is the God of Death's way of maintaining the population that has recently begun to get higher and higher with the war that is happening. When these creatures die, they are judged again by Death and go to a different place, we do not know if it is a good or bad place.

Scions do not kill these creatures to resurrect themselves though, they cleanse them through a spell called Serenity. This brings them back to their humanity and they can either try to resurrect themselves (if their body is still around after all this time) or they can choose to move on to the next Realm. A Necromancer also does not kill these creatures in order to resurrect themselves. They enslave them through a spell called Subjugate. This makes them part of the Necromancer's cache of creatures that they can summon and use to fight their enemies in the Living Realm. They will follow the Necromancer's orders and when they die in the Living Realm they are brought back to the cache in Limbo and can't be summoned until they recover their energy (1 battle topic).